Forecast Update For This Evening
Update (3:39 AM): Precipitation has been falling in the area for a couple of hours and we have had several reports of freezing rain in central North Carolina. While I haven’t seen any reports in ENC, precipitation type has been borderline rain/freezing rain just to the west of ENC. Temperatures will be rising this morning removing the possibility of freezing rain to develop in ENC for the rest of the morning. I will keep monitoring any incoming reports to see if there are any reports of freezing rain in ENC though if it hasn’t occurred yet, it is very unlikely to occur now.
The NWS has issued a Freezing Rain Advisory for Greene, Martin, and Pitt Counties for later this evening. Temperatures today have reached the low 30s in northern ENC and upper 30s south and along the coast.
Temperatures this evening will not drop much if any. Surface temperatures this evening could drop some (maybe a couple of degrees) which will bring them close or just below freezing. A combination of dry air and warming temperatures aloft make for a difficult forecast tonight in the northern Coastal Plains.
Before I go further, this discussion is only valid for the areas currently in the advisory. Areas outside of the advisory will not likely see any frozen precipitation issues tonight.
In the two images above, you can see the factors in play with regard to precipitation type confidence. On the forecast sounding, temperatures right at the surface will be at or slightly below freezing at the 4:00 AM time frame. This is around the time the lower atmosphere will be pretty close to being fully saturated. The area that I colored red on that sounding shows temperatures above freezing as you go up in height. These temperatures there aren’t just barely above freezing, it is roughly 10C (~12F) in a span of 2,000 feet. The forecast map below shows warmer air at that level rushing northward over top of the very shallow cold layer. This obviously isn’t a very friendly environment for frozen precipitation. However, the depth of the cold air at the surface will determine whether the precipitation that we receive is freezing rain or just rain.
You also have to ask: how dry will the air be at the onset of precipitation? The cold air will be retreating tonight and warm air will quickly follow as it does. The atmosphere will have to become more saturated for precipitation to reach the ground. If the atmosphere cannot saturate enough before the below freezing air retreats, the chance for freezing rain is eliminated and we will see just rain. In my forecast leading to today, I have expressed my doubts that the atmosphere will not be fully saturated early enough to support freezing rain. Even though I still have those reservations, the National Weather Service has issued a Freezing Rain Advisory since the chance does indeed exist for freezing rain and I agree with their assessment (even though it doesn’t matter whether I do or not).
So if you are out tonight, drive safely and continue to monitor conditions before you drive to make sure there are no hazards. Monitor the NWS radio for any further official information regarding this weather event.
Update: Areas in central North Carolina will have a slightly deeper cold layer at the surface and will take longer to warm to above freezing temperatures. Even with a delayed onset of precipitation, the colder air may linger long enough for the lower levels to fully saturate to the point where precipitation will make it to the ground as freezing rain. Duration and amount will depend on onset.
If there is, in fact, freezing rain later tonight, the warm air will be quick to replace the cold air and any precipitation will become liquid and remain liquid through the remainder of the weekend.
There will be a break in the rain between Saturday afternoon and Sunday afternoon before the cold front. Most of the rain will occur after the passage of the cold front (anafront type).
Temperatures Saturday and Sunday will rise very fast and very high for this time of year. We are basically going from low and mid 30s tonight to mid to upper 70s in 36 hours! That is roughly about a 40 degree increase in temperatures…in December! The record high for Greenville is 80 so we could in fact come close to setting a record that has been in place since 1921.
Hope everyone has a great weekend and I will have a few more items posted before I logoff tonight.
